The proposed research will examine the underlying cellular mechanisms of immunosuppression associated with chronic African trypanosomiasis. Specific B lymphocyte, T lymphocyte, and macrophage cell functions will be assessed in mice at various stages of infection. Conclusions will be made concerning the level of immunosuppression (i.e., whether B, T, or macrophage cells are affected), the nature of the immunosuppression (i.e., whether it is passive or active), and the cause of immunosuppression (i.e., what parasite-associated mechanisms are responsible for induction). Elucidation of the specific cellular mechanisms involved in immunosuppression and lymphocyte dysfunction in African trypanosomiasis may ultimately enable researchers to block or correct the deficiencies by immunotherapeutic means.